In general, since a variable reluctance motor does not use magnets, as opposed to synchronous motors, it has a simple construction and may be cheaply fabricated. The method of use of this type of motor is as follows: The coil is wound around the poles of the stator; by passing a rectangular wave current, the poles of the stator are excited; the magnetic attraction force pulls the poles of the rotor and causes rotation.
Nevertheless, during rotation, a variable reluctance motor suffers from the problem of nonlinear changes in the magnetic permeance in accordance with the relative positions of the poles of the rotor and stator, and thus the generation of torque ripple. Further, rectangular wave currents include higher order high harmonics, and when the rotational speed becomes high, it is no longer possible to pass the required current due to the difference in the frequency response of the high harmonics. Therefore, it is difficult to use a variable reluctance motor for torque control, speed control, and position control.